In order to precisely position a wellbore a driller must have accurate and real-time information regarding the position and movement of the drilling assembly, information regarding the subterranean formations and the ability to control the drilling assembly. To accomplish these goals bottom-hole assemblies (“BHA”) commonly include various combinations of measurement while drilling (“MWD”) and logging while drilling (“LWD”) techniques and systems. In general, MWD systems collect data such as dip and inclination of the drilling assembly and LWD systems collect data associated with formation characteristics for formation evaluation. For convenience, an instrument combination that includes LWD and MWD systems will be referred to hereinafter as MWD systems. Bottom-hole assemblies also commonly include drilling tools such as a steering system.
The MWD system and/or steering system are typically wired to a surface telemetry system for transmitting signals containing data obtained downhole to the surface and for receiving command signals from the surface. A typical surface telemetry system utilizes mud-pulse telemetry. In this method, a modulator consisting of a rotary valve operates on a continuous pressure wave in the mud column. By changing the phase of the signal (frequency modulation) and detecting these changes, a signal can be transmitted between the surface and the downhole tools. Often modulators and receivers are position at the surface, for example in the mud pump discharge line, and in the BHA so the data and commands can be transmitted between the surface and the BHA.
It has been realized that there are situations in which the complete span of the BHA cannot be wired to transmit data via wiring to the surface telemetry system. This typically occurs when one or more of the BHA sections cannot be practically or feasibly through-wired. One common example of a wired-communication gap in the BHA is in rotary steerable drilling systems. In these systems a mud motor is included in the BHA. The mud motor typically cannot feasibly provide through-wiring to transmit data between the surface telemetry system and the drilling tool that provides inclination data and/or steering control. One solution is to position the various sensors and tools above the mud motor for connection with the surface telemetry system. However, this configuration does not provide the data necessary for precise well placement. Other tools such as, without limitation, reamers, filters, stabilizers, and drill collars also create wired-communications gaps in the BHA. These wired-communication gaps severely limit BHA configuration options and the ability to precisely control and position and wellbore.
Therefore, it is a desire to provide a wireless telemetry system that addresses drawbacks of the prior art MWD systems. It is a still further desire to provide a wireless telemetry system for communicating between wellbore tools and systems. It is a still further desire to provide a wireless telemetry system that bridges wired-communication gaps in a BHA.